<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
            width: 200px;
            height: 200px;
           border: 1px solid red;
           position: relative;
           left: 20px;
           top: 20px;
        }
        .box::before{
            content: '11';
           
        }
        .box::after{
            content: '';
            border: 20px solid red;
            border-top-color: transparent;
            border-right-color: transparent;
            border-bottom-color: transparent;
            position: absolute;
            top: 50px;
            right: -40px;
        }
    </style>
</head>
<body>
    <div class="box">

    </div>
</body>
</html>